The present invention relates to mold casting and, more particularly, to an apparatus for adding material into a stream of molten metal as it is poured into a mold.
It is known to feed various materials or additives into a stream of molten metal for a variety of purposes. In the steel manufacturing industry, for example, compressed air has been used to inject powdered aluminum into molten steel as it is poured from a ladle into a mold. However, prior known systems tend to be inaccurate and wasteful of the additive material because the amount of material to be added is not accurately measured and finely controlled to correlate to the specific amount of molten metal being cast.
In the manufacture of nodular graphite cast iron or gray iron, it has been common to add an inoculant to the molten metal, in order to cause nucleation of the graphite in the iron, either in the pouring ladle or in the mold itself. Proper nucleation of the graphite in the iron provides uniform microstructures that in turn provide more consistent mechanical properties of the iron casting. See, for example, U.S. Pat. No. 4,352,605 entitled "Means for Adding Materials to a Flowing Stream". Coating the mold with inoculant or adding inoculant in the ladle have been found to be unsatisfactory practices. Coating the mold with inoculant produces uneven nucleation of the graphite in the iron. Addition of inoculant when the molten metal is in the ladle is wasteful as an appreciable amount of the full effect of the added inoculant is not realized due to oxidation of the inoculant before the molten metal reaches the mold. Still another unsatisfactory method consists of placing a selected amount of inoculant in the mold opening to be absorbed up by the molten metal as it enters the mold. However, this latter method also leads to sporadic distribution of the inoculant within the molten material, thereby producing a nonuniform microstructure within the casting.
It has been found that better and more consistent results are produced, with a lesser quantity of inoculant, if the inoculant is added as late as possible to the molten stream but before the molten stream reaches the mold. See, for example, U.S. Pat. No. 4,352,605 entitled "Means for Adding Materials to a Flowing Stream". The apparatus of that patent, however, incorporates expensive optical or heat sensing components which do not provide accurate measuring of the inoculant to achieve optimum utilization of the inoculant. Thus, while it is desirous to have a device which adds inoculant to a molten stream prior to addition to the mold, it is also desirous to have a device which predetermines the amount of inoculant to be added into the molten stream and accurately measures the amount of inoculant to be added into the molten stream. It is further desirable that the measuring and adding of inoculant be automatically conducted in order to make the addition process as efficient and economical as possible.
Accordingly, it is an object of the present invention to provide an apparatus for automatically adding an accurately predetermined amount of inoculant into a molten stream just before the molten stream enters the mold. The addition of an accurate predetermined amount of inoculant achieves uniform castings while in turn reducing the frequency of casting rejects. The present invention also provides an apparatus which is adjustably programmable to add a desired amount of inoculant to the molten metal stream, over the pouring period of the mold, on a mold by mold or pour by pour basis. The present invention further provides for injection of the inoculant into the molten metal stream prior to the entrance into the mold, either adjacent to the molten metal stream or through the ladle pouring stopper rod.
From the subsequent detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.